Internal combustion engines are commonly used on mobile platforms (to propel vehicles), in remote areas (such as for oil well pumps or electric generators) or in lawn and garden tools (lawnmowers, etc.). There are various types of internal combustion engines. Spark type engines utilize a volatile fuel, such as gasoline. A spark plug provides the source of ignition. A typical fuel is gasoline, or in high performance engines, methanol. Compression type engines take in air and compress it to generate the heat necessary to ignite the fuel. Typical compression engines utilize diesel fuel.
When gasoline is burned, it produces pollutants in the form of hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO) and soot (particulates). In addition, gasoline in warm climates tends to evaporate due to the presence of volatile organic compounds (VOCs).
Internal combustion diesel engines are commonly used in vehicles. When diesel is burned, it produces pollutants in the form of hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO) and soot (particulates). Nitrogen oxides and volatile organic components react together in sunlight to form ground level ozone, a component of smog. Diesel has less of a tendency to evaporate than does gasoline.
In areas of high use, such as heavy automobile traffic, the emissions from the tail pipes of internal combustion engines and the evaporation from the fuel tanks result in significant air pollution. In some urban areas, a brown haze of pollution frequently hugs the first few hundred feet off of the ground.
Alcohol fuel additives have come into use for internal combustion engines in order to reduce harmful emissions. In the 1970's, gasohol, a blend of mostly gasoline with some ethanol, was introduced during the Arab oil crisis to extend supplies of gasoline. Unfortunately, at that time, many of the elastomeric engine components were designed only for gasoline or diesel and deteriorated with the use of ethanol. Since then, engines have become equipped with fluorinated elastomers, which are more tolerant to alcohol fuels.
Today, the primary alcohol fuel is ethanol, which is typically made synthetically or from grain (corn, wheat, barley, oats, etc.) in a fermentation process. The ethanol is blended into gasoline in various quantities. “Premium” gasoline, with a higher octane rating than “regular” gasoline, is primarily gasoline with 10% ethanol(C2 alcohol). Another ethanol fuel is E-85, which is 85% ethanol and 15% gasoline. Still another alcohol fuel is M-85, which is 85% methanol (C1 alcohol) and 15% gasoline.
Grain ethanol is expensive to produce. Furthermore, producing sufficient quantities of grain ethanol to satisfy the needs of the transportation industry is not practical because food crops are diverted into fuel. Traditionally, grain ethanol has been heavily subsidized by government. Droughts and government policy towards farming in general (less intervention and payments to farmers) make the supply of grain ethanol uncertain and expensive.
In addition, both methanol and ethanol have a relatively low energy content when compared to gasoline. A motorist notices this when a vehicle running on gasoline achieves more miles per gallon than does a similar vehicle running on alcohol fuels.
Some time ago, in the United States, lead was added to gasoline to boost the octane rating. The octane rating relates to antiknock properties of gasoline. Lead has now been eliminated from gasoline for environmental reasons. For the past twenty years or so, gasoline sold in the United States has been blended with 5-15% methyl-tertiary-butyl-ether (MTBE), an oyxgenate, in order to raise the octane rating and to reduce environmentally harmful exhaust emissions. Unfortunately, MTBE is itself a pollutant, having an objectionable odor and taste and having been classified as a potential human carcinogen. To make matters worse, many gasoline storage tanks have developed leaks. MTBE is highly soluble in water and is low in biodegradability. MTBE features a trinary carbon bond which is difficult for natural organisms, such as bacteria, to break down. Consequently, MTBE has polluted the ground water in many communities. Several states, including California, are phasing out the use of MTBE. The phase out will result in an eventual ban.
The planned replacement for MTBE is grain ethanol, but as discussed above, producing the necessary quantities of grain ethanol to replace MTBE is problematic.
Therefore an effective replacement for MTBE in gasoline is needed. In addition, a diesel fuel having fewer harmful emissions, such as particulate soot, is needed. Furthermore, an alcohol fuel that is produced independently of farm products and with a higher energy content is needed.